1. Field of the Invention
The present invention relates to a chlorosilanes purifying apparatus for removing aluminum chloride from a gas containing chlorosilanes such as trichlorosilane produced by a reaction between metallurgical grade silicon and hydrogen chloride and a chlorosilanes manufacturing method.
Priority is claimed on Japanese Patent Application No. 2008-076367, filed on 24 Mar, 2008, the content of which is incorporated herein by reference.
2. Description of the Related Art
Trichlorosilane used as a raw material for manufacturing polycrystalline silicon is manufactured by a reaction between metallurgical grade silicon powder and hydrogen chloride gas in a chlorination reactor, and a higher purity is obtained through a multi-step distillation. In the gas generated in the chlorination reactor, in addition to the produced trichlorosilane, silicon tetrachloride, hydrogen, and hydrogen chloride as unreacted gas are contained. In addition, fine powder of the metallurgical grade silicon used as the raw material and metallic chlorides generated by reactions of impurities (Fe, Al, Ti, Ni, and the like) in the metallurgical grade silicon are also contained.
Among the metallic chlorides, although aluminum chloride (AlCl3) has a relatively low sublimation point (183° C./2.5 atm), aluminum chloride easily solidifies when the system after chlorination is in an atmosphere at the sublimation point or less, and the solidified aluminum chloride deposits in a tank, pipe, or the like in the following processes and becomes the cause of blockage or corrosion. Therefore, conventionally, for example, methods of periodically withdrawing a sediment from the bottom of a distillation column in a subsequent process of the chlorination reactor, using metallurgical grade silicon having an extremely low aluminum density as a raw material, or the like have been employed (see Japanese Unexamined Patent Application Publication No. 2006-1804).